Efficient polymer composites based on natural wool

ABSTRACT

A reinforced polymer composite, and more particularly, a wool reinforced polymer composite is provided. The composition includes wool fibers combined with a polymer to form a reinforced polymeric matrix having at least one of improved Izod Impact Strength (ASTM D-256) or improved Tensile Strength (ASTM D-1708) as compared to the polymer without the fibers.

FIELD OF THE INVENTION

The invention relates to a reinforced polymer composite, and moreparticularly, to a wool reinforced polymer composite.

BACKGROUND OF THE INVENTION

Fiber reinforced polymer composites (FRPC) are class of engineeringmaterials which are extensively suited for advanced applications such asautomotive, civil infrastructure, and military applications.Conventional fibers used to reinforce polymer matrices, such as carbonor glass fibers, are expensive and in some instances their preparationor use may be harmful to the environment. In addition, formulation ofFRPC using such fibers requires state of art equipment and advancedmethods for fiber preparation and coupling, to ensure good bonding ofthe fibrous materials to the polymer matrix.

It would be advantageous if less expensive and less environmentallyproblematic reinforcing materials could be found to enhance themechanical strength of polymeric matrices.

SUMMARY OF THE INVENTION

In a first aspect of the invention, a composition comprises wool fiberscombined with a polymer to form a reinforced polymeric matrix having atleast one of improved Izod Impact Strength (ASTM D-256) or improvedTensile Strength (ASTM D-1708) as compared to the polymer without thefibers.

In another aspect of the invention processes of preparing a reinforcedpolymer composite is provided, by solution casting, solution blending,or melt blending a mixture of wool fibers and a polymer.

In another aspect of the invention, an article of manufacture isprovided which comprises a reinforced polymer composite of reinforcingwool fibers disposed within a polymeric matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described in the detailed description whichfollows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.

FIGS. 1A-1C illustrate different geometries for incorporation of woolfibers into a polymeric matrix;

FIG. 2 is a picture of sheep's wool as received;

FIG. 3 is a picture of chopped wool fibers;

FIG. 4 is a picture of a chopped wool fiber/polymer blend;

FIG. 5 is a picture of continuous wool fibers in a polymer matrix;

FIG. 6 is a graph illustrating the Izod Impact Strength of chopped woolfiber/polymer blends as compared to fiber loading;

FIG. 7 is a graph illustrating Izod Impact Strength of continuous woolfiber/polymer blends as compared to fiber loading; and

FIG. 8 is a graph illustrating the Tensile Strength of chopped woolfibers/polymer blends as compared to fiber loading.

DETAILED DESCRIPTION OF THE INVENTION

The invention describes methods of making polymer/wool composites.Instead of using expensive fibers such as carbon fibers, and relativelyexpensive ones such as glass fibers, sheep's wool was used as a naturalfiber to unexpectedly increase the strength of polymer matrices. Thewool reinforcing fibers are often encountered as waste, which isproduced in huge quantities, especially in Saudi Arabia during theannual season of Hajj, when pilgrimage and non-pilgrimages are performedby sacrificing sheep and the like. Thus, the present invention isadvantageous in not only incorporating less expensive fibers as suitablefor reinforcing polymer matrices, but also in providing an avenue forwaste disposal.

The prepared polymer/natural wool composites are demonstrated to haveexcellent mechanical properties. For instance polymer composites basedon up to 15 wt % of the wool fibers can raise the strength three-fold ascompared to the unreinforced polymers. Polymeric matrices useful in thisinvention are melt processable thermoplastics, e.g. polystyrene (PS),polyethylene (PE), polypropylene (PP), polyester, polyethyleneterephthalate (PET), polycarbonate, acrylonitrile-butadiene-styrene(ABS), thermoplastic elastomers, ethylenepropylenediene (EPDM),polyacrylates, polyvinylchloride (PVC), and polyamide. Howeverthermosets, such as epoxies, vinyl esters, polybenzoxazine, andpolyimides may also be used.

The orientation of wool fibers in the polymer matrices according to thepresent invention is not particularly limited. For example, FIGS. 1A and1B illustrate differing geometries for woven, continuous wool fibersdisposed in a polymer matrix, and FIG. 1C illustrates a geometry forchopped wool fibers disposed in a polymer matrix.

Sheep's wool fiber as it is received is depicted in FIG. 2, and has adiameter of between about 30 to about 150 micrometers, in lengths fromabout 30 mm and about 100 mm. Upon receipt, the wool can be used as-is,or chopped into smaller pieces, such as from about 0.1 mm and about 1 mmin length. Advantageously, either the chopped wool fibers or thecontinuous wool fibers are incorporated into a polymer melt or solutionat levels from about 1 wt % to about 15 wt %, or from about 5 wt % toabout 15 wt %, or even from about 5 wt % to about 10 wt %, based on thetotal weight of the polymer/fiber composite, in order to achieve thebenefits of the present invention.

Methods of composite preparation include, but are not limited tosolution casting, melt blending, solution blending, etc. Those skilledin the art know that thermosetting polymers are not generally meltprocessable, and therefore when making composites according to thepresent invention with thermosetting polymers, solution casting orsolution blending methods can be used, wherein the thermosetting polymeris dissolved in a suitable solvent prior to blending with the fibers.

As previously stated, significant increases in various mechanicalproperties can be achieved according to the present invention. Forexample, in FIG. 6 it is noted that Izod Impact Strength (ASTM D-256)increases significantly for polymer matrices having chopped wool fibersincorporated therein, as compared to the unblended polymer. According tothe data in FIG. 6, unblended polystyrene has an Izod Impact Strength ofonly about 20 J/m; but a polystyrene matrix having 5 wt % chopped woolfiber loading demonstrates an increase in Izod Impact Strength togreater than about 25 J/m, up to about 26 J/m, and when 15 wt % choppedfibers are blended with the polystyrene, the Izod Impact Strengthincreases to greater than about 40 J/m, even to about 42 J/m.

FIG. 7 demonstrates even greater increases in Izod Impact Strength forpolymer matrices blended with continuous wool fibers, as compared to theunblended polymer. Again, the unblended polystyrene has an Izod ImpactStrength of only about 20 J/m; but a polystyrene matrix having 5 wt %continuous wool fiber loading demonstrates an increase in Izod ImpactStrength up to about 32 J/m, and when 15 wt % continuous wool fibers areblended with the polystyrene, the Izod Impact Strength increases toabout 65 J/m.

However, increased Izod Impact Strength is not the only benefit of thepresent invention. FIG. 8 demonstrates significant increases in TensileStrength (ASTM D-1708) of polymer matrices blended with a little as 5 wt% chopped wool fibers, as compared to the unblended polymer. Unblendedpolyethylene demonstrates a Tensile Strength of only about 18.75 MPa,whereas a polyethylene matrix containing as little as 5 wt % choppedwool fiber loading demonstrates an increase in Tensile Strength up toabove 20 MPa.

Examples

The following examples are provided by way of illustration and are notintended to be exhaustive or otherwise limiting to the claimedinvention.

Example 1

Wool was chopped into small size fibers (approximately 0.11 mm inlength) using a grinder with blade cutter suitable for fibrous materials(IKA MF 10 grinder was used). General purpose polystyrene in pellet formwas ground into small particles (˜0.5 mm). The chopped wool fibers andpolystyrene particles were dry mixed and fed to a lab mini extruder forthe preparation of polymer/wool molten blends. The extrudates were driedin a vacuum oven overnight and then molded into samples suitable forIzod Impact and Tensile Strength tests according to ASTM D-256 and ASTMD-1708, respectively. FIG. 4 depicts a mixture of chopped fibers in apolymer matrix.

Example 2

The same procedure as in Example 1 was performed, but the polymer usedwas high density polyethylene (HDPE).

Example 3

Wool fibers (continuous) and polystyrene powder were put in a mold withdimensions of 100 cm×100 cm×3.5 mm (L×W×D) and melted under compressionusing a hot press. The resulting sheet was cut into samples for IzodImpact Strength measurements. D was the thickness of the mold. FIG. 5depicts a blended matrix of polymer and continuous fibers.

Example 4

The same procedure as in Example 3 was conducted, but the polymer usedwas high density polyethylene (HDPE).

The foregoing examples have been provided for the purpose of explanationand should not be construed as limiting the present invention. While thepresent invention has been described with reference to an exemplaryembodiment. Changes may be made, within the purview of the appendedclaims, without departing from the scope and spirit of the presentinvention in its aspects. Also, although the present invention has beendescribed herein with reference to particular materials and embodiments,the present invention is not intended to be limited to the particularsdisclosed herein; rather, the present invention extends to allfunctionally equivalent structures, methods and uses, such as are withinthe scope of the appended claims.

What is claimed:
 1. A composition comprising wool fibers combined with apolymer to form a reinforced polymeric matrix having at least one ofimproved Izod Impact Strength (ASTM D-256) or improved Tensile Strength(ASTM D-1708) as compared to the polymer without the fibers.
 2. Thecomposition of claim 1, wherein the wool is sheep's wool.
 3. Thecomposition of claim 1, wherein the wool fibers are woven into a fabricand the fabric is disposed within the polymeric matrix.
 4. Thecomposition of claim 1, wherein the wool fibers are randomly dispersedwithin the polymeric matrix.
 5. The composition of claim 4, wherein thewool fibers have diameters from about 30 to about 150 microns.
 6. Thecomposition of claim 5, wherein the wool fibers are chopped into lengthsof from about 0.1 mm and 1.0 mm.
 7. The composition of claim 5, whereinthe wool fibers have lengths of at least about 30 mm.
 8. The compositionof claim 1, wherein the polymer of the polymeric matrix is athermoplastic polymer selected from the group consisting of polystyrene,polyethylene, polypropylene, polyester, polyethylene terephthalate,polycarbonate, ABS, thermoplastic elastomers, EPDM, polyacrylates,polyvinylchloride, and polyamide.
 9. The composition of claim 1, whereinthe polymer of the polymeric matrix is a thermosetting polymer selectedfrom the group consisting of epoxy, vinyl ester, polybenzoxazine, andpolyimide.
 10. The composition of claim 1, wherein the wool fibers arepresent in an amount of between about 1 and about 15 wt % based on theweight of the composition.
 11. The composition of claim 1, having atensile strength greater than about 20 MPa.
 12. The composition of claim1, having an Izod Impact Strength greater than about 25 J/m.
 13. Aprocess of preparing a reinforced polymer composite, comprising solutioncasting a mixture of wool fibers and a polymer in solution.
 14. Aprocess of preparing a reinforced polymer composite, comprising meltblending a mixture of wool fibers with a molten polymer.
 15. A processof preparing a reinforced polymer composite, comprising solutionblending a mixture of wool fibers and a polymer in solution.
 16. Anarticle of manufacture, comprising a reinforced polymer composite ofreinforcing wool fibers disposed within a polymeric matrix.